Our daily schedule of waking and sleeping is timed by a body clock known as a Circadian Rhythm. Each night sleep is also has a rhythm of its own running through five stages, recognisable by EEG (electroencephalogram, measuring electrical activity in the brain) recording.

If our Circadian Rhythm is out of synchronisation (eg due to flights across time-zones or due to unusual sleeping patterns) we may find that when we physically want to sleep may not be when we psychologically want to sleep.

The Stages of Sleep

Stage 1:

During this light sleep, which lasts about two minutes you, may experience fantastic images like hallucinations. You may experience a sense of falling at which moment you may suddenly jerk (Myoclonus) or feel as though you are floating or weightless.

It is during the first few stages of sleep that many people encounter some difficulty at some stage during their lives (30% ++). We lie awake thinking about going to sleep and become frustrated that we seem to be incapable of doing so. This is the experience that we often label as "insomnia". Thankfully there are a number of solutions that do not require chemical sedation.

Stage 2:

As you relax more deeply you begin a period of around twenty minutes of stage 2 sleep characterised by the periodic occurrence of spindle bursts - bursts of rapid brain activity. Sleep talking may occur at this stage of sleep and you can still be awoken without much difficulty.

Stages 3-4:

The next few minutes you proceed through stage 3 and into stage 4 (deep sleep). Together, these stages are categorised as Slow Wave sleep, when your brain emits delta waves. This phase lasts for about thirty minutes, during which you are hard to awaken. During this deep sleep we may begin walking, or as children wet the bed. Even when we are deeply asleep our brains somehow process meaningful stimuli allowing us to move around in our beds without falling out. An unusual sound or the crying of a baby may cause us to quickly awaken. EEG recordings confirm that our auditory cortex responds to sound stimuli even in deep sleep.

About an hour after you fall asleep a strange thing happens; rather than continuing in deep sleep, you begin to ascend through stages 3 - 2 (where you spend about half your night) and enter a phase of sleep called REM.

REM-Phase:

During your first cycle of REM sleep your brain waves become rapid, more like those of nearly awake stage 1 sleep. Unlike stage 1 sleep, during REM your heart rate rises, your breathing becomes more rapid and irregular and every half minute or so your eyes dart around in a momentary burst behind closed eye lids. During REM, your genitals become aroused (erection / vaginal lubrication). The morning erection stems from the last wave of REM Except during very scary dreams genital arousal always occurs, regardless whether the dreams content is sexual.

During REM the motor cortex is active, however your brain stem blocks its messages, leaving your body so relaxed except for the occasional twitch, so that you are essentially paralysed. During this stage it is difficult to awaken and therefore is sometimes referred to as paradoxical sleep. Unlike the fleeting images of stage 1, REM images are usually emotional and story like. Most researchers of dreams do not accept the theory that rapid eye movements indicate the individual is visually scanning the dream, but that eye movements are a result of the dreamers active nervous system.

As the night wears on this sleep cycle repeats itself around every 90 minutes. During the night the deep stage 4 sleep gets progressively shorter and then disappears whilst the REM periods get longer. By morning 20 -25% of our sleep has been spent in REM some 100 minutes per night.

Sometimes when the emotional content of a dream exceeds our ability to process that information we may wake suddenly in the middle of a dream. Sometimes such dreams can reoccur night after night such that our sleep pattern is disrupted and we begin to expect to wake-up during specific dreams at specific times. This can be disrupt our sleep patterns dramatically. There are a number of highly effective theraputic techniques to enable the processing such dreams to be completed such as EMDR.

Why do we dream

In his landmark book 'The Interpretation of Dreams' published in 1900, Freud argued that by fulfilling wishes a dream is a psychic safety valve that harmlessly discharges otherwise unacceptable material. A symbolic representation of unconscious drives that would be threatening if expressed directly. Freud's theories have, however, been surpassed by new theories. One of which is Information Processing, which hypothesises that dreams may help sort, sift and fix in memory our daily experience.

Following stressful periods or intense learning, REM sleep increases. There appears to be compelling evidence that REM sleep facilitates memory. During experimental trials Subjects awoken at the beginning of REM cycles had far greater difficulty recalling certain information verbalised to them prior to sleep, than did those who were not awoken.

Another explanation of dreams is that they serve a physiological function. It is thought that dreams, or the associated brain activity of REM sleep, provide periodic stimulation that develops and preserves the brains neural pathways. Still another physiological theory is that dreams erupt from spontaneous neural activity that spreads upwards from the brainstem, implying that dreams are the brains attempt to make sense of these impulses (our overactive brain weaves a story from whatever impulses are available). It appears that our visual cortex and our emotion related limbic system both become active during REM sleep and hence may affect our dreams.

The underlying function of dreams still creates great debate, but most theorists recognise that we need REM sleep. Individuals who have been deprived of REM sleep, when allowed to sleep naturally rapidly return to REM and spend longer periods in this stage. This phenomenon is known as REM rebound.

This study was aimed to examine the relationship between sleeping positions, dream characteristics, and subjective sleep quality in normal subjects. Sixty-three healthy subjects (45 males and 18 females) were included in the present study. Of these participants, 41 were grouped in right-side sleeping position and 22 subjects were in left-side sleeping position.

The subjects were interviewed in terms of dream recall frequency, vividness, bizarreness, nightmare frequency, and dream emotions suggested by Hartmann et al. PSQI was also administered to the subjects. The rate of nightmare sufferers was significantly higher in left-side sleepers (40.9%) than in right-side sleepers (14.6%).

Relief-safety was more common among right-side sleepers than the others. Global PSQI score were significantly lower in right-side sleepers than left-side sleepers. These findings suggest that dreaming and sleep quality may be affected by body posture.

Research: Sleep loss may increase appetite

Annals of Internal Medicine, December 7, 2004. Dr Van Cauter.

Consistently getting a good night's sleep may be one of the answers to maintaining a healthy weight, if early research findings are correct.

The small study found that when healthy young men slept for only fours hours on two nights in a row, they showed dips in a hormone that suppresses appetite, coupled with increases in an appetite-stimulating hormone. On top of that, the volunteers reported being more hungry after their sleep-deprived nights than after nights when they slept for 10 hours.

The two appetite-regulating hormones in question are leptin, which is released from fat cells and helps alert the brain that it's time to stop eating, and ghrelin, which is produced in the stomach and helps trigger hunger. Van Cauter's team found that when the 12 men in their study slept for four hours on two consecutive nights, their levels of leptin were 18 percent lower and their levels of ghrelin were 28 percent higher than they were after two nights of spending 10 hours in bed.

When the men were asked to assess their appetites after sleep restriction, they showed a 24 percent increase in their "hunger ratings." And the foods they craved most were sweets, salty foods like chips and nuts, and starchy fare like bread and pasta. More about weight control and sleep loss...